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Surge Protection Devices

Discussion in 'Electrics UK' started by Click4, 12 Nov 2012.

  1. Click4

    Click4

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    Hi, just wondered if anybody is using them and opinions...

    I have used MK consumer units before because I felt MK was a good brand, but I've started coming to the realisation they aren't that great..

    So was gonna try a Hager one, when I was looking at them... I came across the fact they do a surge protection kit now for their consumer units.. Even a video on YouTube by hageruk.

    In 17th edition Amendment 1 it states a risk assessment should be carried out, and if the risk assessment deems it necessary a surge protection device should be fitted.. Looks like that was one of the changes in amendment 1

    But when I looked into that hager kit, not only can I not find anywhere that stocks them.. In fact only CEF even list them on their site. But they carry a hefty £200 price tag for the kit from what I can assertain.

    With ever increasing amount of electronic devices in our homes, laptops, pcs, flat screen tvs, games consoles, sky/virgin boxes... DVD/blu-ray players, hifi equipment.. Potentially added up to thousands... Is it worth taking the risk not having a surge protection device? Does saving your equipment justify the £200 price tag?
     
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  3. JohnW2

    JohnW2

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    If one knew the level of risk (i.e.probability) of such items of equipment beiong damaged by surges, then it would be an easy cost-benefit calculation. As things are, I don't really think we have a clue as to the true level of risk - but I strongly suspect that it is extremely low. I might wildly guess that more items get damaged by having drinks poured over them, and probably far more as the result of actions of small children!

    Another relevant part of the calculation is that, as technology (and fashions!) goes forwards in leaps and bounds, many/most of the items of equipment you mention become very rapidly 'obsolete', and are often replaced long before the end of their natural lives. Steps taken to improve average life-expectancy of the items may therefore have less real impact than one might imagine.

    Kind Regards, John
     
  4. Click4

    Click4

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  5. JohnW2

    JohnW2

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    Well, you could make some wild guesses and do the sums. Say that the average household has £5,000 of such equipment (probably a pretty high estimate) and that the risk of death of all that equipment due to a surge in any year is 1 in 5,000 (probably very much higher than the true risk). Then, the cost of equipment damaged by surges would average at £1 per year ... so go figure :) Of course, if you had £1m worth iof equipment, then the arithmetic would change dramatically.

    Have you personally, or anyone you know or have heard of, ever experienced loss of any such equipment which was definitely (or even 'very probably') due to a 'surge'?

    Kind Regards, John.
     
  6. Click4

    Click4

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    If I am correct.. twice, lol but once I cant be sure as it was just an assumption.

    First time, was a local transformer substation exploded.. which killed a £4k computer server motherboard.

    2nd time, to me anyway it seemed a bit iffy that somebody I know of had their virgin media box replaced at the same time as their TV which said to me some kind of power surge likely did the 2 devices in.. but not confirmed and cant be sure.

    probably a higher risk if fed from overhead cables.

    I always use surge protectors in the house, for the computers and TV personally, surge protector costs about £25-30 each for a good quality Belkin one... use them also because they have multi plugs on them.
     
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  8. JohnW2

    JohnW2

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    Unless what happened to the substation was a secondary effect (i.e. it was also the victim of a surge), I doubt whether that was a 'surge' in the sense of BS7671, and very probably not something that an SPD would have offered protection against.
    As you say, not at all certain.
    Definitely. In fact, the SPDs described in Section 534 of Amd 1 of BS7671 seem to be only intended to protect against surges due to lightning and related atmospheric phenomenon.
    A lot of people do use them, and a fortune has been made out of selling them. Call me a sceptic or cynic if you wish, but I am yet to be convinced that any of them have ever 'saved' a single bit of equipment - and the amount that has been spent on them could have bought a lot more, useful, equipment!

    Kind Regards, John
     
  9. Click4

    Click4

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    lol, I can pretty much confirm they dont work.

    Despite my post asking about the usefullness of Surge Protection devices and using one myself.

    That £4k Server was plugged into a Belkin Surge Protector at the time of the exploding substation... but it could be like you said lightening effects it differently.
     
  10. viewer

    viewer

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    There's some general info here:
    en.wikipedia.org/wiki/Surge_protector
    and, as it points out, the surge protector only works on the electrical supply so a lightning induced surge affecting the aerial inputs to TV, Sky boxes etc would still see them go up in smoke.
     
  11. bernardgreen

    bernardgreen

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    The exxploding substation could have thrown the voltage on the network neutral high above ground potential which would result in high currents from all CPC's ( "earth" wires ) to ground through anything that connected the CPC to a grounded item. Two routes for these high currents are TV aerial leads to aerials on wet walls and telephone cables where the isolation barrier in the equipment fails under the fault voltage on the CPC. The equipment then fails due to the high current flowing through it. 100 mA in the worng place will destroy electronic equipment.

    Lightning strikes do the damage by raising the local ground voltage high above the voltage on the network neutral with the same result of high currents flowing from CPCs to ground through equipment.

    Surge protectors cannot prevent damage in these situations.
     
  12. SimonH2

    SimonH2

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    "Plug in" SPDs may well offer little protection - and can actually make matters worse.

    "Whole House" protection is definitely the correct way to go, BUT to be effective, then everything must go through the same set of protective devices - phone line, TV/Sat antenna cables, cable TV cable, ...
    Note that this means that (for example) your phone line must go to the common protection point and then onwards to where it's needed. Having a separate protective device across the house and bonding it won't help (much) as even a 10mm2 cable presents a fairly high impedance to the fast rise time transients present in lightning induced spikes.

    People are correct to say you need to consider the risk. Where I live we are fairly OK - thunder isn't common and we have underground electric and phone services. On the other hand, at my last job I know the boss lost quite a bit of kit to lightning - and that's less than 10 miles away. The difference is that his house was in the country with overhead power and phones.
    It was invariably things like faxes and answering machines (or cordless phone bases) that went. Being connected between the phone line and the mains meant there was a route for surges from the phone line, through the equipment, to mains earth - while non-powered phones were seldom affected as there wasn't a route for the surge to take to ground through the device.
    I suggested they should fit some surge protection, but they didn't fancy routing the phone cable right round the house and back again - and note that the "outside" part of the circuit should never be near anything on the "inside" (where "outside" and "inside" are with respect to the protection devices).


    The most spectacular failure I saw the effects of was to a portable setup in Madagascar - yes, as a computer dealer in Cumbria, we had a customer in Madagascar :confused: Apparently that part of the world is very bad for thunder storms - and he was in a real belter of one when things went off with a bang.
    I reckon the spike came in through the phone line - into the built in modem. Blew the modem chip to bits and arced over to the main board of the portable. Then via the serial lead, the printer, and the printer's power supply, to mains earth. The case of the printer power supply physically opened up - blew a hole in the case you could stick a finger through (if daft enough !).

    Customer was "not very happy", and was even more annoyed that both the cheap phone, and the desk light, survived unharmed :rolleyes: Because they were only connected to one system, they were immune from the common mode surges.
     
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